High speed locking clamp

ABSTRACT

A securing/clamping system for use with platens of a molding machine including a stationary platen having a first mold half affixed thereto, a movable platen having a second mold half affixed thereto, the movable platen travelling along a plurality of tiebars, and reciprocatively moving between a mold open and mold closed position, and a system for applying a clamping force to the movable platen.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 08/997,314, filed Dec. 23, 1997, which in turn is aContinuation-In-Part of U.S. patent application Ser. No. 08/743,719,filed Nov. 6, 1996, now abandoned, which is a 371 of PCT/US97/19507filed Oct. 29, 1997.

BACKGROUND OF THE INVENTION

The present invention relates to a securing/clamping system for use withplatens of a molding machine, especially an injection molding machine.

The prior art includes many injection molding machines which use tie barclamping units for positioning a platen for the application of clamp-upforces. Control systems using hydraulic fluid, pressurized air andelectric motors in combination with numerous switches and typically acontroller unit are used to control both the positioning of the platensand the application and removal of clamp-up force for acquiring moldclamp-up and mold break.

Japanese Patent 61-261017 discloses a clamping mechanism for injectionmolding machines. The purpose of the control system therein is tomaintain a parallel parting line between the molds by sensing thedistance traveled by each clamping cylinder of each tie bar andmaintaining the distances substantially equal. Accordingly, parallelismof the parting line between the molds can be maintained when theinjection pressure of molten resin is uneven within the mold.

U.S. Pat. No. 4,832,884 to Speck et al. discloses a method for measuringand controlling the closing force of a plastic injection moldingmachine. Accordingly, for an injection molding machine, a closing forceis measured for a predetermined number of operation cycles. A mean valueis calculated from the measurements and if the mean value is within apredetermined tolerance, no control intervention takes place. However,if the mean value is outside the tolerance but within a zone limited byalarm units, control intervention takes place by stepwise changing theinstalled height of the mold until the actual value measured for closingforce after each operating cycle is within the tolerance given. In thismethod and system, a toggle joint system serves to generate the closingforce on the first and second mold parts. In this case, the force ismeasured and if the force is within a tolerance zone, the spacingbetween the first and second mold parts is altered to less than or noincrease relative the old force.

U.S. Pat. No. 4,966,738 to Inaba et al. discloses a method for moldclamping force adjustment. Accordingly, in this method, a mold touchposition is detected, at which the mold halves of a mold contact eachother. The mold temperature is detected by means of thermocouplesattached to the mold halves. The mold thickness is obtained based on theposition where a movable platen and a stationary platen of the injectionmolding machine contact each other. After a molding operation isstarted, the mold temperature is detected and the amount of change inmold thickness during a period between a preceding cycle and a currentcycle is calculated based on the change of mold temperature, the moldthickness, and the thermal expansion coefficient of the mold. A moldtouch position for a current cycle is obtained based on the calculatedvalue. Accordingly, when the mold is clamped in the current cycle, themovable platen is moved from the mold touch position toward thestationary platen by a predetermined amount to produce a predeterminedmold clamping force. For this method, the measurements and adjustmentsare directed primarily to the mold position and not to the position ofthe clamping units. A clamping unit is a singular one which functions toforce the movable platen against the stationary platen. That is, no tiebar clamping units are used internal to any of the platens for producingthe clamp-up force.

U.S. Pat. No. 5,147,661 to Kurumaji et al. discloses a mold aligningdevice for a compression molding machine. The mold aligning deviceincludes a plurality of mold position adjusting cylinder actuatorsdisposed on a bed wherein position detectors are associated with themold positioning adjusting cylinder actuators to detect the strokesthereof. The hydraulic source for driving the mold position adjustingcylinder actuators and control unit for controlling the strokes of thepiston rods of the actuators with reference to zero points of the pistonrods of the actuators, is determined beforehand. The zero points aredecided by placing the upper mold in close contact with the lower moldand extending the piston rods of the actuators so that the piston rodsare pressed against the lower surface of a slide block. The strokes ofthe piston rods are controlled during a compression-molding operation sothat the upper mold is maintained precisely in parallel with the lowermold. This device is directed to pressure molding. The cylinderactuators are not positioned within a movable molten platen, and theactuators do not clamp onto tie bars. The main purpose of the machine isto maintain parallelism between the upper and lower molds by theactuators placing direct pressure on the upper mold supporting surfacefor maintaining the same parallel to the lower mold.

U.S. Pat. No. 5,338,171 to Hayakawa et al. discloses a die-clampingapparatus with an aligning device. The apparatus includes a stationarydie plate for holding a stationary die, a movable die plate for holdinga movable die, a hydraulic cylinder for moving the movable die plateforwardly and rearwardly with respect to the stationary die plate, and atie bar for clamping by a fastening device located in the movable dieplate. One or more alignment devices are provided so as to join themovable die and the stationary die in such a manner that primaryalignment can be performed. The molding apparatus can be provided with aguide pin for secondarily aligning the movable die with respect to thestationary die when the stationary die and the movable die have beenplaced at predetermined positions. Four die clamping cylinders areprovided at the corners of the stationary die plate so as to apply aclamping force to the stationary and movable dies after the fasteningdevice has fastened to the tie bar. For this device, the tie barfastener and clamping units, while being located on the tie bars, oneadjacent the movable platen and one adjacent the stationary platen, areseparate devices adding to the complexity of the machine.

U.S. Pat. No. 5,370,518 to Sasaki et al. discloses an apparatus forinjection and compression molding. The apparatus includes and injectiondevice and a compression molding device wherein the compression moldingdevice includes a stationary die plate for holding a stationary die, amovable die plate for holding a movable die, means for rapidly extendingand retracting the movable die plate relative to the stationary dieplate and means for locking the movable die plate to the tie bars at aposition where the movable die plate approaches the stationary dieplate. Means for fastening the dies after the movable die plate islocked to the tie bars is also provided. An injection device for feedinga molten plastic material into a mold cavity between the stationary dieand the movable die initiates feeding of the molten plastic materialinto the mold cavity when the stationary die and movable die are partedfrom each other by a predetermined distance. The plastic material iscompressed and drawn while the movable die is moved towards thestationary die after a predetermined quantity of molten plastic materialhas been fed into the mold cavity. The apparatus includes a device in amovable die plate for clamping onto the tie bars. However, the devicedoes not include a combined means for providing the clamping forcebetween the platens and fastening to the tie bars, as the clamp force isprovided by separate die fastening cylinders which are positioned on thetie bars but separate from the fasteners.

U.S. Pat. No. 5,133,655 to Schad et al. shows a clamp mechanism for aninjection molding machine in which four columns attached to the movingplaten are individually gripped by fluid actuated cylinders which alsoact as clamp force pistons. While this design is effective, it requiresvery close tolerances to be maintained between the columns and the innerbores of the cylinders since the amount of deflection of the cylinderwalls to achieve sufficient gripping on the columns is small. Thus,manufacturing this clamp is expensive and in operation maintaining thesesmall clearances imposes costly maintenance procedures.

U.S. Pat. Nos. 5,624,695, 5,645,875 and 5,620,723 to Glaesener show anovel lock nut arrangement for engaging the tiebars of a two plateninjection molding machine clamp, for example. The locking nuts also actas clamp force pistons acting on the tiebars to clamp the mold betweenthe platens.

It is an object of the present invention to provide a fast acting,energy efficient injection molding machine clamp assembly.

It is a still further object of the present invention to provide aninjection molding machine clamp assembly with a vertical clampconfiguration and with low construction cost, low maintenance and goodreliability.

It is a still further object of the present invention to provide aninjection molding machine clamp assembly with a vertical clampconfiguration which occupies less floor space than conventional designs.

Further objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

In accordance with the present invention, the foregoing objects andadvantages are readily obtained.

The present invention provides a vertical securing/clamping system foruse with platens of a molding machine, especially an injection moldingmachine. The system of the present invention includes a stationaryplaten having a first mold half affixed thereto and a movable platenhaving a second mold half affixed thereto, with the movable platentravelling along a plurality of vertical tiebars. Means are provided forvertically reciprocatingly moving the movable platen between a mold openand a mold closed position. The present invention includes means forapplying a clamping force to the movable platen in the mold closedposition comprising at least one vertical column having a first endaffixed to the movable platen and a second end spaced from the movableplaten with a plurality of vertically oriented, spaced teeth on thesecond end, a clamp piston adjacent the second end of the column, andvertically oriented lock means as lock nuts engaging the clamp pistonoperative to engage and disengage the circumferentially spaced teeth.The aforesaid vertical orientation provides significant advantages overother vertical clamps. For example, the build height (length) of theinstant clamp is relatively small, allowing the overall height of theinjection molding machine to be lower and fit in low ceiling buildings,which is a significant advantage. Moreover, the instant machine isparticularly suitable for producing compact discs (CD's).

Further features of the present invention will appear hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understood from aconsideration of the following illustrative drawings, wherein:

FIG. 1 is a section view of a clamp mechanism of the present invention;

FIG. 2 is a detailed section view of a locking nut of the presentinvention;

FIG. 3 is a perspective view of a locking nut and bearing assembly ofthe present invention;

FIG. 4 is a section view of an alternate embodiment of a clamp mechanismof the present invention;

FIG. 5 is a section view of an additional alternate embodiment of aclamp mechanism of the present invention;

FIG. 6 is a section view showing an alternate embodiment of a clampmechanism of the present invention; and

FIG. 7 is a section view showing the vertical clamp configuration of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a high speed clamp mechanism 10 foran injection molding machine including a fixed platen 12, a movableplaten 14 and a clamp block 16. Tiebars 18 connect fixed platen 12 andclamp block 16 while supporting the movable platen 14 which is free toslide along the tiebars. Generally four of the tiebars are used withonly two being shown in FIG. 1. Moving platen 14 is moved from a moldclosed position shown in FIG. 1 to a mold open position by cylinders 20which may be supported by clamp block 16. One cylinder 20 is shown inFIG. 1, but of course two or more of the cylinders may be used dependingon requirements. The cylinders are actuated by a suitable motive means,not shown.

First mold half 22, such as a cavity half, is affixed to movable platen14, and second mold half 24, such as a core half, is affixed to fixedplaten 12, with the mold halves together forming mold 26 in the moldclosed position. As indicated above, movable platen 14 moves on tiebars18 between a mold open and mold closed position. Only one mold 26 isshown in FIG. 1 for simplicity, but naturally a plurality of the moldscan readily be provided.

Attached to the back side of movable platen 14, i.e., the movable platenside opposed to mold 26, is at least one column 28, generally aplurality of columns and preferably four columns, with two of thecolumns shown in FIG. 1. Columns 28 have a first end 30 affixed tomovable platen 14 and a second end 32 spaced from the movable platen. Aplurality of teeth 34 are provided on second end 32. Circumferentiallyspaced between teeth 34 is at least one axial groove 36 and generallythree or more of said grooves as clearly shown in FIG. 3. Columns 28pass through corresponding holes 38 in clamp piston 40, with the clamppiston 40 housed in clamp block 16 as shown in FIG. 1. Bearing 42 inclamp piston 40 support the columns in holes 38.

Lock nuts 44 mounted on or with clamp piston 40 and carrying lock nutteeth 45 are rotatable to engage or disengage teeth 34 on column 28. Thelock nuts may be any desired locking means and engage clamp piston 40 orare retained inside or on a face of clamp piston 40, as by bearings 42as shown in FIGS. 2, 3 and 5, or by retaining caps 46 as shown in FIGS.1 and 4. Clamp piston 40 is retained inside clamp block 16 by front cap48 or other desired retaining means. Lock nuts 44 are caused to rotateby cylinder 50 via linkage 52. In an alternate embodiment shown in FIG.4, lock nuts 44 have gear teeth 54 cut in their external perimeter andthese are engaged by a central gear 56 which is driven by motor 58 viadrive shaft 60 that passes through clamp piston 40. The shaft 60 issplined so that it can move axially with respect to motor 58 when theclamp piston 40 carrying gear 56 moves within clamp block 16.

Sleeves 62, which can be an integral part of lock nut 44 as shown inFIGS. 2 and 5, or separate pieces as shown in FIGS. 1 and 4, use seals64 to prevent fluid in the clamp cylinder from escaping duringoperation.

Ejector plate 66 carry ejector pins 68, is mounted on columns 28 toeject molded articles from mold 26 in a conventional manner.

In operation, movable platen 14 carrying first mold half 22 is moved tothe mold closed position shown in FIG. 1 to form mold 26 by cylinder(s)20. Lock nuts 44 are rotated so that lock nut teeth 45 engage columnteeth 34. High pressure fluid is directed into clamp cylinders 41 tocause clamp piston 40 to press against lock nuts 44 and thereby againstcolumns 28. This action clamps mold 26 between fixed platen 12 andmovable platen 14. After injection and cooling of the plastic iscomplete the clamp is opened by first directing pressurized fluidagainst the "mold break" side of clamp piston 40 into cavity 70. Thiscauses clamp piston 40 to pull lock nuts 44 away from the movable platen14, they act on the back side of teeth 34 on column 28 and cause mold 26to be forced open a short distance. Next, the lock nuts 44 are rotatedout of engagement with columns 28, and cylinders 20 complete the openingof the mold. The molded parts are ejected from the mold 26 in aconventional manner and the clamp is ready to repeat the cycle.

The alternate embodiment of FIG. 6 shows a single column 72 having afirst end 74 affixed to movable platen 14 and a second end 76 spacedfrom the movable platen. Column 72 is provided with a plurality of teeth78 adjacent second end 76 which may be along the length of column 72 asshown in FIG. 6. Teeth 78 engage corresponding teeth 80 in bore 82through single clamp piston 84 in locked relationship as shown in FIG.6. Clamp piston 84 is rotated to engage/disengage teeth 78 and 80 bycylinder 86 which may be mounted onto clamp block 88. Teeth 78 on column72 are interrupted by slots as shown in the other embodiments, see slots36 in FIG. 3, so that in the disengaged position the teeth 80 in piston84 are cleared in the slot permitting column 72 to move freely throughbore 82 in piston 84. Column 72 is fixed to the back of movable platen14, as by bolts 90, which is moved to open and close by cylinders 92(one shown in FIG. 6). Cylinder 92 is mounted to moving platen 14 andits rod 94 is mounted to clamp block 88. Alternatively, the cylinder maybe mounted to the clamp block and the rod to the moving platen. Theoperation of the embodiment of FIG. 6 is essentially as the previousembodiments. An advantage of the embodiment of FIG. 6 is its reducedcost and greater simplicity and hence greater reliability.

FIG. 7 shows the vertical clamp configuration of the present invention.The vertical clamp assembly shown in FIG. 7 includes clamp block 100mounted on base 102. Clamp piston 104 is housed in clamp block 100 andthe clamp piston is rotated by cylinder 106. Vertical column 108 passesthrough central hole 110 in clamp piston 104 and is bolted to movableplaten 112 which slides vertically on vertical tiebars 114. Naturallymore than one column may be used if desired. One of said tiebars 114 isshown in FIG. 7, but naturally a plurality are desirably used and threeare used on the machine of FIG. 7. Stationary platen 116 is fastened tothe top of tiebars 114 and mold 118 is situated between the platens asin the other embodiments. The moving platen 112 is verticallyreciprocated by center cylinder 120 inside column 108 and containingcenter piston 122, the rod side of which is mounted on base 102.

FIG. 7 shows the clamp in the closed position. In operation, movingplaten 112 is moved vertically upward to close mold 118 by means ofcylinder 120. When mold 118 is closed, cylinder 106 causes clamp piston104 to rotate, as for example 45 degrees, to engage vertically orientedclamp piston teeth 124 with corresponding teeth 126 on column 108, asdescribed for the previous embodiments. The clamp piston 104 is urgedupward by introducing high pressure oil into clamp cylinder 128 thusclamping the mold.

To open the mold 118, high pressure oil is introduced into mold breakcylinder 130 causing the clamp piston to move downward pulling themoving platen 112 downward by acting on the backside of clamp pistonteeth 124. When the clamp piston 104 bottoms on clamp block 100,cylinder 106 causes clamp piston 104 to rotate and disengage teeth 124from column 108. Oil is then introduced into cylinder 132 causing movingplaten 112 to move downward and open mold 118.

The design of the clamping system of the present invention uses verylittle pressurized fluid to cause its motions for securing and clampingand consequently is a very energy efficient and fast acting clampsystem.

The simplicity of the system of the present invention has the advantagesof low construction cost, less maintenance and good operatingreliability when compared to conventional systems. When compared to aconventional column blocking style of clamp design, the present designis smaller, lighter and less costly components are mounted on the clamppiston face. Also, the distance between the back face of the movingplaten and the front face of the clamp block can be reduced withoutreducing platen opening stroke because the shutter plate assembly hasbeen eliminated. Thus, the overall build length of the present clampsystem is shorter and thereby reduces the footprint of the clamp whichreduces the required floor space in the operating plant. Also thevertical clamp configuration of the present invention offers significantadvantages over other vertical clamp designs.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

What is claimed is:
 1. A vertical securing/clamping system for use withplatens of a molding machine, which comprises:a stationary platen havinga first mold half affixed thereto; a movable platen having a second moldhalf affixed thereto, said movable platen travelling along a pluralityof vertical tiebars; means for vertically reciprocatingly moving saidmovable platen between a mold open and a mold closed position; means forapplying a clamping force to said movable platen in the mold closedposition comprising at least one vertical column having a first endaffixed to the movable platen and a second end spaced from the movableplaten, with a plurality of circumferentially spaced, verticallyoriented teeth on said second end, a clamp piston adjacent the secondend of the column, and vertically oriented lock means engaging the clamppiston operative to engage and disengage the circumferentially spacedteeth wherein in the clamped position the clamp piston presses againstthe lock means which in turn presses against said column.
 2. The systemof claim 1, wherein said clamp piston is vertically movable to clamp andunclamp the mold halves.
 3. The system of claim 1, including a singlecolumn.
 4. The system of claim 1, including a plurality ofcircumferentially spaced, vertically oriented teeth on the clamp pistonwhich engage teeth on said column.
 5. The system of claim 4, whereinsaid clamp piston is housed in a clamp block and said column passesthrough a corresponding hole in said clamp piston.
 6. The systemaccording to claim 5, wherein said column includes at least one verticalaxial groove circumferentially spaced between the teeth.
 7. The systemaccording to claim 6, including means to rotate the clamp piston toengage and disengage the clamp piston teeth and the column teeth.
 8. Thesystem according to claim 1, wherein said column is spaced from saidtiebars.